Numerical studies on a type of mechanical stirring in directional solidification method of multicrystalline silicon for photovoltaic applications

Influence of Mechanical Stirring on the Crucible Dissolution Rate and Impurities Distribution in Directional Solidification of Multicrystalline Silicon

“…As it was shown previously [13], mechanical stirring can be a good option for improving the melt flow in large crucibles even for smaller values of the stirring's rotation rate. The influences of the mechanical stirring were investigated on both melt convection and interface shape, but there is no analysis on impurities distribution and crucible dissolution rates.…”

“…In a previous study [13], the influence of the same type of stirrer on the solid-liquid interface and on the melt convection has been investigated for different values of the stirrer's rotation rate. It was found that, as the rotation frequency increases, the melt mixing is improved both horizontally and vertically.…”

“…A detailed description of the model was presented in [13] and it mainly consists of the following assumptions:…”

“…The presence of carbon and nitrogen in the silicon melt during the directional solidification process, can lead to the formation of SiC and Si 3 N 4 precipitates [4,5,6,7,8,9] which can determine the appearance of dislocations and cracks during the wafer sawing of the ingot. In order to improve the impurity segregation and to obtain a uniform distribution of impurities in the melt, different techniques were proposed to control the melt flow in a directional solidification configuration: use of travelling magnetic fields [10,11], use of a combination of vertical magnetic field and electrical current [12] or a mechanical stirring [13]. Besides the beneficial influence on the impurity distribution, one should also take into account the influence of the forced convection on the solid-liquid interface and on the crucible dissolution.…”

“…The influences of the mechanical stirring were investigated on both melt convection and interface shape, but there is no analysis on impurities distribution and crucible dissolution rates. Because these influences are of crucial importance for the applications, it is the aim of this paper to continue the investigation on mechanical stirring from [13] with focus on impurities distribution and crucible dissolution rates.…”